Universal joint with bellows seal and vent

ABSTRACT

A bellows seal for a universal joint has its sleeve surrounding the drive shaft separated from this shaft over only a cylindrical segment by a device communicating between the interior of the sleeve and the external atmosphere. This device has a portion of small circumferential width lying below the sleeve and a portion of large circumferential width integral with the first portion. An axial groove in the first portion communicating with a meandering groove forming a baffle in the second portion before this meandering groove opens into the ambient atmosphere.

FIELD OF THE INVENTION

The present invention relates to a universal joint of the typecomprising an inner element fixed to a driving shaft, an outer elementcooperating with the inner element and fixed with a driven shaft, and atight casing in the form of bellows whose ends are respectively fixed tothe driving shaft and to the outer element.

BACKGROUND OF THE INVENTION

When a universal joint of this type operates, there are variations intemperature which lead in particular to an increase in the pressureinside the joint and a deformation of the tight casing; suchdeformation, which is increased by the effect of the centrifugal forceon the grease in the joint, tends to cause rapid deterioration of thetight casing.

To overcome this drawback, joints have been made in which the spaceinside the casing was connected to the atmosphere by a device interposedbetween the driving shaft and the casing and provided to this end withan inner groove.

For example, French Pat. No. 2 414 145 describes a universal joint inwhich the device for communicating with the atmosphere is constituted bya split elastic ring which is disposed between the tight casing and thedriving shaft and is shaped so as to leave an air passage along thedriving shaft when the sleeve of the casing is clamped on this shaft.

However, this device for communicating with the atmosphere has a numberof drawbacks. When the driving shaft does not present a groove where thebellows is held, the elastic ring which has a relatively low coefficientof friction, less than that of the casing, may slide on the drivingshaft. Furthermore, in the case of sliding universal joints in which theinner volume of the joint may vary rapidly, the grease contained in thecasing may emerge through the groove of the ring.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a universal jointprovided with a device for communicating with the atmosphere whichovercomes the drawbacks which have just been set forth.

SUMMARY OF THE INVENTION

According to the present invention, the device for communicating withthe atmosphere is constituted by an element which is in the form of aportion of a cylinder and whose inner face comprises a groove presentinga baffle.

When the element in the form of a portion of a cylinder is interposedbetween the driving shaft and the casing, the contact between the rubberof the casing and the metal of the shaft is conserved over the majorpart of the circumference of the shaft. Said element is therefore heldperfectly and cannot slide. The baffle with which the groove is providedavoids leakages of grease.

In a particular embodiment of the invention, the element forcommunicating with the atmosphere presents a zone of larger width on theinner face of which the baffle is formed, and a zone of smaller width onthe inner face of which the groove extends axially; this groovepreferably opens out via two grooves extending substantially in a planeperpendicular to the longitudinal direction of the element.

The element for communicating with the atmosphere may comprise, on theouter face of its zone of smaller width, a groove in which thecorresponding end of the tight casing is maintained clamped.

The outer face of the zone of larger width of the element may comprise agroove in which is engaged a clamping band maintaining the elementclamped on the driving shaft.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be more readily understood on reading the followingdescription with reference to the accompanying drawing, in which:

FIG. 1 is a view in axial section of the universal joint according tothe invention;

FIG. 2 shows an internal view of the device for communicating with theatmosphere;

FIG. 3 is a view in longitudinal section, the element for communicatingwith the atmosphere being cut along line III--III of FIG. 2.

FIG. 4 is an end view of the element for communicating with theatmosphere;

FIG. 5 is an external plan view which shows the device for communicatingwith the atmosphere.

SPECIFIC DESCRIPTION

Referring now to the drawings, FIG. 1 shows the universal joint, in thiscase of the RZEPPA type, which comprises an inner element 1 fixed on ashaft 2 and provided on its periphery with grooves 3 in which balls 4are engaged. The latter are maintained in a cage 5 and engaged,furthermore, in grooves 6 formed on the inner face of an outer element 7of the joint, in the form of a bowl, which is fixed on the second shaft8 of the joint.

A protecting casing 9 in the form of bellows, made of elastomer, has atone of its ends a fixing sleeve 10 engaged in a groove 11 in the outerelement 7 and maintained in position by a clamping collar 12. At itsother end, the casing has a fixing sleeve 13 which is fixed on the shaft2 by a clamping collar 14, with the interposition of an element 15 forcommunicating with the atmosphere, made of plastic material.

As may be seen more particularly from FIGS. 2 to 5, the element 15 is inthe form of a portion of a cylinder, i.e. a cylinder segment with aninternal radius virtually equal to the radius of the shaft 2 andcomprises a zone 15a of greater width and a zone 15b of smaller width.On the inner face lying in contact with the shaft 2 of the axiallyextending portion 15b of smaller width is made a groove 16 which, in thezone of small width 15b is axial, and opens out into two perpendicular(transverse) grooves 17 and 17'. In the zone 15a of large width, thegroove has the form of a baffle 18, i.e. manders from side to sidebefore opening axially to the outside.

The outer face of the zone 15b of small width is formed with a groove 19in which the fixing sleeve 13 is disposed. On the outer face of the zone15a of larger width is formed with a groove 20 in which is disposed aclamping collar or band 21 maintaining the end of the element 15 clampedon shaft 2, to avoid detachment of the element 15 under the effect ofthe centrifugal force. The element 15 may also be clamped on shaft 2 bythe two tongues moulded with the element, which are circular in form andadapted to be clamped on the shaft by known means such as clippingmeans. Reference 22 denotes recesses made next to the groove 20 andintended to lighten the zone 15a of larger width and to give it greaterflexibility.

When the joint operates, the space inside the bellows 9 communicateswith the atmosphere via groove 16 and grooves 17 and 17'. However, thegrease contained in these bellows is prevented by the baffle 18 fromescaping.

In the claims:
 1. A universal joint comprising:an inner element fixed toa driving shaft; an outer element fixed to a driven shaft and coupledwith said inner element for joint rotation therewith; a bellows sealconnected to one end with said outer element and having a sleeve to anopposite end thereof surrounding said driving shaft and directlycontacting same; and a device communicating between the interior of saidbellows seal and the atmosphere external of said bellows seal, saiddevice comprising a cylindrical segment interposed between only aportion of said sleeve and said driving shaft, said cylindrical segmenthaving an axially extending portion of relatively smallercircumferential width connected to a portion of relatively greatercircumferential width, said segment being provided with an inner surfaceabutting said shaft and formed with a groove open toward said shafthaving a rectilinear axially extending stretch in said axially extendingportion communicating with said interior of said bellows seal and ameandering stretch forming a baffle in said portion of relativelygreater circumferential width communicating with the externalatmosphere.
 2. The universal joint defined in claim 1 wherein saidaxially extending stretch of said groove communicates with the interiorof said bellows seal by a pair of transverse grooves lying substantiallyin a plane perpendicular to the longitudinal dimension of said axiallyextending portion.
 3. The universal joint defined in claim 1 whereinsaid device is composed of a plastic.
 4. The universal joint defined inclaim 1 wherein said portion of relatively greater circumferential widthhas on an outer surface thereof, a second transverse groove receiving aclamping band retaining said cylindrical segment on said driving shaft.5. The universal joint defined in claim 1 wherein said axially extendingportion is formed on an outer surface thereof with a first transversegroove receiving said portion of said sleeve, further comprising meansfor clamping said portion of said sleeve against said axially extendingportion of said cylindrical segment.
 6. The universal joint defined inclaim 5 wherein said portion of relatively greater circumferential widthhas on an outer surface thereof, a second transverse groove receiving aclamping band retaining said cylindrical segment on said driving shaft.